Heretofore a battery pack comprising a plurality of cells each having a safety valve has been known. The safety valve works to release gas to the outside of the cell when internal pressure of the cell exceeds a fixed level due to the gas (hydrogen gas or the like) generated, during charge/discharge. Such battery pack is disclosed in e.g. Patent Document 1. In the battery pack disclosed as an embodiment of the invention in Patent Document 1, a plurality of battery modules (cells), each having a safety valve, is arranged in rows in parallel. Each safety valve is connected with a gas discharge tube to be connected to an external exhaust part. Specifically, the gas discharge tube has a plurality of outlet coupling parts each of which is fit in a gas outlet port of each safety valve for connection with the safety valve. In a battery pack mentioned as a related art in Patent Document 1, a T-shaped joint is placed in the gas outlet port of the safety valve so that both ends of the joint are sequentially connected through gas discharge tubes, thereby forming a gas discharge line to be connected to an external exhaust part.
In the above battery packs, when the internal pressure of the battery module(s) (cell(s)) exceeds the fixed level due to the gas generated during charge/discharge, each safety valve operates to release the gas through the gas outlet port into the gas discharge tube (the gas discharge line). Then, the gas is discharged out of the battery pack through the gas discharge tube (the gas discharge line) and the external exhaust part. In this way, the gas released through each safety valve is collected to be discharged together outside, thus improving measures for safety, for example, to prevent the gas from catching fire.
Patent Document 1: Japanese unexamined patent publication No. 2001-110377